Dimension	Minimum	Maximum
Height	3-1/2 inches	6-1/8 inches
Length	5 inches	11-1/2 inches
Thickness	0.007 inch	1/4 inch

Any item smaller than the minimum dimensions is not mailable.
For larger items, see large envelopes or packages.
For envelopes, length is the dimension parallel to the address.

For items over 3.5 ounces, see large envelope or package prices.

Letters that meet one or more of the nonmachinable characteristics below are subject to the nonmachinable surcharge.

• It is a square letter
• It is too rigid – does not bend easily
• It has clasps, string, buttons, or similar closure devices
• It has an address parallel to the shorter dimension of the letter
• It contains items such as pens that cause the surface to be uneven
• The length divided by height is less than 1.3 or more than 2.5

The minimum size for a square envelope is 5" x 5".
Square letters are subject to the nonmachinable surcharge.